In general, the most widely used method of methods of forming a pattern on a silicon wafer is photolithography using ultraviolet rays and a photoresist. A method of reproducing the most nonoscale pattern is electron beam lithography. In addition, there are methods employing FIB, nanoimprint, sidewall, and so on.
If a single line is formed using only the existing pattern formation method, it generally has several tens of nanometers. A reproducible line width of several nanometers can be obtained using only several methods.
Further, in the case of a multi-line, a space must be placed between lines in order to separate the respective lines. In this case, not only the size of an overall pattern can be increased due to the space, but also the line width of an individual line and the space between the lines are more limited due to the proximity effect, etc. when compared with the single line.
In the event that a pattern having a line width of several tens of nanometers and a relatively simple structure is formed using the existing pattern formation method as described above, there are no particular problems. However, in the case where a multi-pattern having a complicated shape and structure and requiring a very small size due to the level of integration of devices is required, it is practically impossible to obtain a desired producible pattern.
Of the conventional pattern formation methods, electron beam lithography that has been most widely used in nonoscale patterns has the following problems.
1) Electron beam lithography has the greatest efficiency in the number or shape of patterns and a line width, but has the proximity effect occurring neighboring patterns as a width between patterns is narrowed.
2) There is a limit to reduce a width between patterns because of the proximity effect.